@yury25: World of Tanks if you have approximately a week to learn it and understand you can sell tanks to make room for new ones and not have to spend money (which I figured out eventually). But it is a HARD CORE sim game but if you have the time, TURN OFF CHAT, and patience can be extremely rewarding.

Company of Heroes: Tales of Valour (ie the first one) if you are a rts fan (still almost as many playing online as the sequel). Do not look at the sequel, just ignore it and back away slowly.

There is of course 7 Days to Die which is a third person base building zombie defence game.

Wow I was gonna make the same thread. I made so any good friends via L4D2 but grew out of it as it stopped being updated. I went back months ago but it was so empty. I really wish more modern games allowed you to be as social as you could in L4D2 (the open mic in every game was so amazing). Any luck so far?